1. Field
This application generally relates to the field of wireless communication systems, and more particularly to signals and protocols to enhance data transmission efficiency in such systems.
2. Related Art
The subject matter set forth herein is applicable to wireless communication systems generally. However, it has been developed primarily in the context of cellular telecommunication systems, which facilitate high-speed connectivity and data and voice transport on both point-to-point and point-to-multipoint bases. First-generation (analog) and second-generation (digital) cellular networks were used primarily for communicating voice traffic via mobile cellular telephones, and thus maintained a focus on access methods for the efficient transport of voice information. With the rising popularity of the Internet, a third-generation (3G) wideband multimedia cellular network has been proposed that transports both voice and data at much higher speeds than were previously available using the first and second generation wireless networks.
A Third Generation Partnership Project 2 (3GPP2) has been established by industry groups for the purpose of defining specifications to transition current code-division multiple-access (CDMA) wireless networks to the third generation, which is commonly referred to as CDMA2000. One such specification may be referred to as “CDMA2000 1× Revision D” (which may also be referred to as “CDMA2000 1× Rev D,” “cdma2000 Release D,” “IS-2000-D”, or “IS-2000-Rel. D”). The CDMA2000 1× Rev D specification, available from the 3GPP2, is incorporated by reference herein in its entirety for its teachings on communications protocols used in 3G wireless communications systems.
Many proposals of communication protocols for use in CDMA2000 Release D have been submitted to the 3GPP2, including protocols for both forward link transmissions from a base station (BS) to a mobile station (MS), and for reverse link transmissions from an MS to a BS. A relatively new feature that is desired involves multicasting signals from a base station (BS) to a select group of mobile stations (MSs) concurrently. To effect this feature, it is helpful to notify or “wake up” the typically “sleeping” MSs in time to receive the multicast signal. Proposals have recently been set forth that would incorporate one or more Broadcast/Multicast Service (BCMCS) Indicators into a quick paging (QP) channel (QPCH). The QPCH already exists in systems that accord with earlier versions of CDMA.
FIG. 1 illustrates some salient features of a quick paging channel. In a CDMA system, a QPCH may be defined by a particular orthogonal code of length 64 (for example). A QPCH frame 102 is 40 mS long, and typically aligned with (two) 20 mS voice frames. A QPCH frame 102 is typically divided to include about 192 distinct time slots, each having a known relationship to the 20 mS system timing, which in turn bears a known relationship to the serving BS pilot signal. Assuming 192 such slots, 192 different MSs may each have a unique association with one such slot, readily permitting a QPCH frame to serve 192 different users concurrently. However, with hashing protocols, particular slots may be concurrently associated with (and thus serve as paging indications for) a plurality of different MSs. Such hashing practices are well understood, but for simplicity this extension will not be set forth in detail herein. Accordingly, the QPCH slots will in general be treated herein as each associated uniquely with a particular MS, with the understanding that the association may be extended by procedures such as hashing.
Numerous MSs are associated with particular slots in the representative 40 mS QPCH frame 102. Each MS analyzes a signal, at least in the appropriate corresponding slot of the QPCH frame, to determine the information contained in such QPCH message. For legacy MSs, the signal is simply on/off. A signal present on the QPCH at the appropriate time provides a page indication (PI), after receipt of which a legacy receiver will proceed to decode a further message that provides details relevant to such paging. An absence of signal at the appropriate time is an “off” signal, and directs a legacy MS to do nothing other than wait for the next page. In FIG. 1, fifteen different slots are illustrated in the “on” state, i.e., are being actively transmitted, in each frame. This is represented by the fifteen small vertical black boxes 104 (in QPCH frame 102) and 108 (in QPCH frame 106).
In order to enhance reliability, the entire QPCH frame 102 is repeated a second time as duplicate QPCH frame 106. The fifteen actively transmitted slots 108 in the duplicate QPCH frame 106 are disposed in the same relative position with respect to timing of the frame 106 as are the fifteen slots in the first frame 102. Identical relative locations are maintained for convenience and convention.
The proposals thus far presented for adding broadcast/multicast service (BCMCS) indications to the QPCH channel have generally included reserving a few slots within each frame for indicating a multicast for some number of MSs. Each slot would be shared at least with other MSs in the same multicast “group,” and the number of slots available would be distributed among the MSs associated with the QPCH frame to provide all BCMCS indications for such MSs. Thus, for example, a particular MS may be associated with a quick page (QP) message slot at a unique location 110, a multicast slot at a location 112 (shared with some other MSs), and a broadcast slot at a location 114 (the broadcast slot is shared with all MSs associated with the QPCH frame).
These proposals are relatively easy to implement in conjunction with less-capable “legacy” MSs, because the system controller or BS need only avoid assigning legacy MSs to the slots reserved for the new BCMCS Indicator features. However, they have been shown to impair the standby time of idle devices. It has been shown that shared BCMCS Indicators will most likely significantly reduce the standby operating time of an enabled receiver. See, e.g., “BCMCS Indicator,” contribution C30-20031208-xxx to 3GPP2 by Czaja and Qian, the contents of which are hereby incorporated in their entirety by reference. First, most MSs need only about 2.5 mS to wake up, examine a signal, and go back to sleep. Therefore, a need to look at two different locations within a QPCH frame, such as locations 110 and 112, will require waking up twice as often. Because the RF circuitry consumes approximately 50% to 75% of the MS power when it actively monitors an assigned paging slot, it is useful to minimize the amount of time that the MS is active.
Additionally, only a relatively few multicast slot locations are provided. As such, MSs from different multicast groups will share the multicast locations. Consequently, many MSs would receive a BCMCS indication that is not intended for them, requiring such MSs to wake up and decode additional messages. Only after such activity would the awakened MSs determine that the indication is not intended for them. The unnecessary additional waking/receiving time will reduce a standby time capacity of enabled MSs.
The proposals that have been set forth for reserving slots in the QPCH for BCMCS Indicators reflect a need for such extended signaling capability for newer MSs, while preserving compatibility with legacy stations (whether MS or BS). The method set forth herein addresses that need.